SMALL DAMS PETITS BARRAGES

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Fig. 7.2 – Section through an embankment showing rehabilitation with a positive effect both on stability, piping control and seepage control Furthermore, to extend an earthfill core a High Density Polyethylene Sheet may be used to raise the core by anchoring it in a trench excavated in the top of the core. This method is especially applicable where ice conditions occur where the top of the core can be damaged by low temperatures. 7.3.1.3 Protection of Embankment from Erosion During Overtopping Erosion as a result of overflow during flood events is a principal cause of embankment dam failure. Consequently, the approach to solving this problem has been not to allow overtopping. Preventing overtopping of existing dams to accommodate today’s current estimates of inflow floods often requires costly modifications to the spillway or raising of the embankment. For a large number of potentially unsafe dams with inadequate spillway capacity, permitting overtopping during large or infrequent floods would result in significant benefits. If overtopping of an embankment is allowed, the owner of the dam must ensure that the downstream slope is sufficiently protected to prevent erosion. Two erosion protection systems i.e. articulated concrete blocks (ACB) and roller compacted concrete (RCC) are often used successfully for the protection of the downstream face of embankments during floods. (a) Articulated Concrete Blocks An auxiliary spillway constructed with small cable tied concrete blocks system laid on a geotextile base is capable of withstanding velocities less than 8 m/s and provides a low cost alternative to reinforced concrete, as can be seen in Figure 7.3 and 7.4. Care should be taken to design for lower velocities of up to maximum 5 m/s (say) to accommodate deteriorating (or ageing) conditions during the life of the dam. 118
Fig. 7.3 – Installation of the articulated concrete blocks in a channel Fig. 7.4 – Lateral slopes protected with concrete blocks and grass This is the primary conclusion drawn from a series of tests undertaken in the UK by the Construction Industry Research & Information Association (CIRIA). The research has been prompted by the Reservoir Act 1975 which requires local authorities to enforce safety provisions on reservoirs with capacities greater than 25 000 m 3 . These trials have also attracted interest from all over the world with inquiries coming from Australia, Israel, Peru and Chile, and, most interestingly, the US Bureau of Reclamation (BuRec) which is facing similar upgrading problems to the UK. 119
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SMALL DAMS Design, Surveillance and
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FOREWORD The ICOLD - International
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ACKNOWLEDGEMENT The Ad Hoc Committe
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FOREWORD ACKNOWLEDGEMENT SUMMARY TA
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5.5.5 Compaction in confined areas
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7.2.1 Introduction 7.2.2 Spillway c
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1. SMALL DAMS DEFINITION AND CLASSI
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2 Fig. 1.2 - Relationship H . V wit
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1.3 REFERENCES [1] French Committe
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2.3 ZONED EARTHFILL DAMS In arid pa
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sloping core guarantees water impou
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Fig. 2.11 - Hlinky Concrete Gravity
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Fig. 2.13 - Photograph of Neusberg
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The gabion dam as the gabion retain
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Some inflatable dams are operated b
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3.1 INTRODUCTION 3. SAFETY OF SMALL
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Condition Effect on safety 13. Dama
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Fig. 3.2 - Massive dam break overto
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and suffusion or internal instabili
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downstream part of the embankment m
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small dam impounding a lot of water
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Whenever the Supervising Authority
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emergency management organizations
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c) The decommissioning plan should
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5.1 INTRODUCTION 5. FEATURES OF THE
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5.2 DESIGN FLOODS Inadequate flood
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downstream slope will show seepage
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Fig. 5.2 - Design Freeboard 5.4.3 F
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2 U f Fe S 1400 D Where Uf is the d
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Maximum compaction is obtained at c
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characteristic must be determined.
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5.6.1 Foundation Watertightness The
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� A continuous vertical chimney d
Page 67 and 68: Thickness of pervious layer Thick D
Page 69 and 70: t 5.7.1.4 Practical Considerations
Page 71 and 72: It is generally accepted that cohes
Page 73 and 74: � Simple Bishop (1955) � Spence
Page 75 and 76: � The elements for surface draina
Page 77 and 78: The supporting layer for the rip-ra
Page 79 and 80: For very small reservoirs (fetch of
Page 81 and 82: The junction of the downstream slop
Page 83 and 84: Fig. 5.14 - Hongshiyan homogenous d
Page 85 and 86: material has been left in place or
Page 87 and 88: The homogeneous dam is recommended
Page 89 and 90: [3] OL and OH soils are not recomme
Page 91 and 92: part (core) lies in the zone (Fig.
Page 93 and 94: 6. GUIDELINES ON SURVEILLANCE OF SM
Page 95 and 96: cases the owner may retain the serv
Page 97 and 98: Surface displacement on an embankme
Page 99 and 100: Fig. 6.1 - Leakage measurement usin
Page 101 and 102: Water Level Sounder - Details of th
Page 103 and 104: pressure) Left abutment 2 5 Weir ga
Page 105 and 106: Fig. 6.9 - Recommended standpipe pi
Page 107 and 108: the others weir gauges need to be i
Page 109 and 110: � Earthquakes sensible at the dam
Page 111 and 112: APPENDIX INSPECTION CHECKLIST FOR S
Page 113 and 114: Exposed reinforcement � The condu
Page 115 and 116: These spillways can be lined or unl
Page 117: flowing water. Flowing water with h
Page 121 and 122: Fig. 7.7 - Dam overtopping protecti
Page 123 and 124: complete construction was in 2001,
Page 125 and 126: In some cases, the downstream face
Page 127 and 128: Tube-a-manchettes injection system
Page 129 and 130: 7.3.5 Slope Protection Measures 7.3
Page 131 and 132: Pipe Rehabilitation SLIPLINING MODI
Page 133 and 134: Conditions Pros Cons Comments types
Page 135 and 136: Embankment dams that have properly
Page 137 and 138: and minimize erosion. Design of sui
Page 139 and 140: [20] SMEC- “Draft Guidelines for
Page 141 and 142: present visual information. It must
Page 143 and 144: Fig. 8.1 - Three small dams in casc
Page 145 and 146: Social Disruption low (rural area)
Page 147 and 148: Fig. 8.4 - Flood water level after
Page 149: 8.9 REFERENCES [1] BURREC (1994) -
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SMALL DAMS PETITS BARRAGES

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